Sharif Digital Repository

Numerous studies have shown a direct relationship between skeletal muscle active force and intracellular calcium ion concentrations; In fact, no matter how the muscle is stimulated (neurological, electrical, chemical, and mechanical stimuli), the main cause of muscle activation and consequently force generation is calcium ions.According to this scientific finding, the purpose of this study is to present a new chemo-mechanical multiscale model of skeletal muscle based on the fundamental principles of continuum thermodynamics. In this model, unlike other similar studies, muscle active force is not considered as the conventional multiplication of isometric force in a set of corrective... 

Optical impairments, as a challenging obstacle in optical communication systems, have been under deep attention of optical engineers in recent years. These impairments can be divided into two categories of linear and nonlinear impairments. Dispersion is a significant linear impairment leads to broadening of the optical signal and interference between transmitted symbols during detection. Nonlinear impairments such as cross-phase modulation (XPM) and self-phase modulation (SPM) also distort the transmitted signal through the fiber, causing interference at the receiver and degrading the system's performance. An appropriate solution for compensating optical fiber impairments is to utilize... 

Our body makes use of many degrees of freedom in muscle space. As a result, there are many solutions for activating muscles when performing a specific task. “how our central nervous system (CNS) controls abundant degrees of freedom?” has been a popular question for researchers in the field of motor control since Bernstein. The existence of muscle synergies is one of the proposed hypothesis, and there is experimental evidence that they are encoded in our CNS as building blocks. The aim of this study is to study the effect of training on the number, structures, and activation profiles of muscle synergies that are used for maintaining balance. For this purpose, electromyography data from 28... 

Environmental destructive effects of gases caused by combustion of sulfur compounds in the fuel, poisoning of catalysts, corrosion of equipment, as well as intensification of environmental considerations and new standards adopted for maximum sulfur content has made the desulfurization of fuels important; The desulfurization method using hydrogen has a high potential to remove sulfur. One of the major challenges in this process is to find the proper catalyst that has the best performance for this process. Ni (or Co) Mo (or W)/ γ-Al2O3 catalysts have high potential for using as a catalyst for the desulfurization process from a variety of large-scale or industrial hydrocarbon cuts. According to... 

Results showed that 9 factors of “Brand Equity”, “Product Quality”, “Service Quality”, “Service Recovery”, “Perceived Value”, “Relationship”, “Employee Satisfaction”, “Physical Environment” and “Distribution Channel” are most effective factors by researchers that have effect on customer satisfaction. Thus, the Macromodel of this research was designed based on these factors. Due to limitations and context of the research, “Service Quality”, “Service Recovery” and “Relationship” were chosen in the final model. Results of questionnaire showed that the 5 parameters of “Service Recovery Speed”, “Reliability”, “Responsiveness”, “Empathy” and “Seller-focused antecedents” was the most important... 

In this thesis, the thermal and thermoelectric properties of graphene-based nanostructures are numerically investigated. The transport parameters, including Seebeck coefficient, electrical conductance, and thermal conductance are obtained as well as the thermoelectric figure of merit. The Hamiltonian matrix is set up using a third nearestneighbor atomistic tight-binding approximation and the dynamical matrix using a 4th nearest neighbor force constant approximation. Both ballistic and diffusive regimes are considered in this work. For transport investigation, the Landauer formula and the nonequilibrium Green’s function techniques are used. The role of temperature, geometrical parameters,... 

In this project a complete simulator for a two-winding, 25cm air gap Maglev system by considering the pratical constaritns, position and velocity observer and the current sensor dynamics was derived. In order to control the ball in any desired position a twisting sliding mode controller was designed as the basic controller in the rest of project. The designed controller can not transfer the ball in far trajectory. In first step we modify that to reach a better performance by changing the value of current, passing through the coils in steady state. In the second step, the far trajectories are divided to a finite number of sub-trajectory such that the ball can pass these sub-trajectory by... 

Systems that are electrostatically actuated have found a vast role in MEMS application. This technology is used in optical systems, sensors, micro switches, and deformable mirrors. Raising the use of these systems in fields that needs better performance highlighted the need to accurate study of dynamics and control of electrostatic actuated systems in micro scale. This work is dedicated to design of an estimation and control system for a micro-beam that is actuated by electrostatic. After a comprehensive survey on pervious works that are done on dynamic, applications, fabrication and control of these systems dynamic of the system is fully derived. The environmental factors like fringing... 

In this thesis, the theory of robust control is applied to design a controller for hover flight of a tail-sitter unmanned aerial vehicle with 2 ducted-fan propulsion. The control surface deflection (in propeller slipstream) is considered as the input controller of the system. The aircraft dynamical model is developed based on the assumption of no aerodynamic loads on other parts of uav in low speed flight associated with the hovering condition. The controller is primarily designed using both classical and modern control techniques. Then H ∞ and µ synthesis approaches are applied to design the robust controller. The results obtained from different approaches are compared. It is shown that... 

With new progresses in technology, a growing need to power energy has emerged. In Iran most of power plants are far from cities and therefore expansion of power network will cause long transmission lines with high capacities which connect power plants to cities. There are three solutions for these kinds of lines: 1) two-circuit transmission lines 2) higher voltages 3) new forms of transmission lines (HVDC and compact). In this thesis some of these suggestions have been analyzed to find the best solution for a 560 Km transmission line in Iran.
Designing transmission lines has a lot of steps which all are related to each other. In this project a comprehensive algorithm has been utilized to... 

Sulfur compounds are largely an impurity in fossil fuels such as natural gas, crude oil and coal. In natural gas, the main sulfur compounds are hydrogen sulfide (H2S), carbonyl sulfide (COS),and C1-C3 mercaptans.Commercial methods for removing these compounds require the introduction of additional reactive substances (O2, H2, Olefins, NaOH, etc.), which often results in the production of other pollutants. Microfluid is a branch of science and technology that involves studying the behavior of fluid, the use of fluid and the manufacture of equipment or systems that are carried out in micro-channels.The dimensions of these canals are about ten to several hundred micrometers, and high of... 

Small and medium-sized businesses in all countries are an important part of the economy, but are strongly affected by rapid changes in the external environment, especially demographic and economic. These rapid changes are affecting the marketing of these businesses to meet customers' needs and expectations in order to maintain a competitive position in the market. Startups, as a group of small and medium-sized businesses, are no exception and are affected by the changes. To respond to these changes startups need to have a proper marketing strategy in order to survive failure in this dynamic environment. The marketing strategy of these organizations is different from the marketing strategy... 

Conjugated linoleic acid (CLA) is a collective term used to describe the mixture of geometric isomers of linoleic acid which has several beneficial biological effects. Considering the use of CLA for medicinal of nutraceutical purposes, an isomer-selective and safe process is required. The introduction of biological reactions to CLA production will solve this problems. Nowadays, CLA is produced through chemical isomerization of linoleic acid which results in by-production of unexpected isomers. From this point of view biotechnology methods and producing microorganisms implementation have gained lots of attention because of not producing unwanted bypass products and also being natural method.... 

Wearable robots, or exoskeletons, are electromechanical devices that aim to assist user by supplying additional mechanical power as needed. The interaction of these robots with humans and the possibility of robots using their various abilities such as intelligence, control power, sensors, etc., make one of the crucial components of these control algorithms, its interaction and integration with the user. In this regard, functional electrical stimulation is one way to use human abilities to control the robot and achieve broader goals. Adding functional electrical stimulation to a wearable robot creates an emerging group of robots called hybrid exoskeletons. Hybrid exoskeletons provide the... 

Road accidents are unfortunate events that cause more thanl16000 deaths each year in Iran. Intercity accidents require a comprehensive plan to reduce casualties because the number of roads users are increasing and the accidents account for nearlyl65% of fatalities. In this study, we first tried to identify the status of Iran through a study of traffic accidents in the world, and then the research and activities carried out in Iran were analyzed to find new and effective solutions. Using the daily fatalities data froml2008 tol2014, and using the new methodology presented in this research based on the Discrete Fourier Transformation (DFT), the Box-Jenkins models and the Secant method, the... 

Production of copper-zirconium amorphous alloys by mechanical alloying and the process of changing crystal structure to amorphous, was examined. The amount of progress of amorphization has been checked by x-ray analysis after different hours of milling. By increasing the percentage of zirconium in this type of alloy, the process of amorphization has been improved. But There is a limiting factor which is due to the tendency of zirconium to produce oxide and nitride phase. Also, the effect of excessive elements on crystal structure changing has been checked. Hence, adding elements like nickel or aluminum has a different effect on the process of amorphization. adding aluminum to the system... 

Due to the fast speed of changes in sciences and living conditions, concepts undergo a transformation as time goes by. Accordingly, the academic updating of such concepts in a way that is in line with the immediate perceptions of society seems necessary. The concept of luxury goods has changed a lot since old times. To understand how society perceives luxury goods, the current study aimed to make a thorough review of the past studies and investigate the characteristics of luxury goods. Then, the extracted characterizes were investigated on 355 participants by distributing questionnaires randomly. While selecting the characteristics, more emphasis was put on their innateness and the... 

In most radio receivers like superheterodyne receivers, a weak desired incoming signal is accompanied with many interferer signals that are much more powerful than the desired signal itself. These interferers, also called blockers, can cause a great disturbance in the functionality of the receiver. Due to gain compression and an increase in the noise figure (NF) of the receiver, the blockers should be filtered before the arrival at the output of the LNA. Because of the low quality factors of the available on chip inductors and in order to eliminate the out of band interferer signals and image frequency (in superheterodyne receivers), usually an external surface acoustic wave (SAW) filter is... 

In the recent years, cloud data center issues have been the center of attention. Also for them topologies with multi paths between end hosts are offered. For use of multi path traffic engineering is essential. Researches show congestion occurred in the cloud data center networks, because the mean of link utilization is down. This means, some of links are congested while there are some other with much available bandwidth. Currently, the most common method is Equal Cost Multipath (ECMP) algorithm for routing flows in the data center network. ECMP decides on routing without any attention to network congestion condition. There, may be two big flows placed in the one path and it causes creation... 

Demand estimation has always been one of the most important components of marketing in all industries. Because the profitability of any organization depends on the demand for the product or service that the organization offers to the market. On the other hand, in order to optimize the performance of the organization and better planning, we need to have an estimate of demand in order to avoid wasting the available facilities by optimally allocating resources. Another issue that shows the importance of demand estimation is the dependence of optimal pricing on the amount of demand, which can be said to be the most important tool of the organization to manage its revenue. Optimal pricing can be...